My truck started off with a slight vibration now it has increased severely. It vibrates in all gears. Park, drive, reverse. It vibrates so bad even my dashboard rattles. The spark plugs & engine mounts have been replaced and there is no engine light on. I took it to a mechanic and they cannot find the problem. Please help besides this issue the truck runs great.
My car has 100000 miles.
My car has an automatic transmission.
If a motor vibrates while in park idling, there is either a balance issue with the motor or an engine mount problem. Locating such problems is not for the faint of heart. There are several techniques that can be done, mostly using a large pry bar to apply tension one mount at a time. When you do this with a mount and the vibration changes significantly, then you have found the mount that is the problem.
With that said, your Envoy has a few things that commonly cause this problem. The engine and transmission mounts will cause this. If the engine mounts are found to be the problem, they need to be factory parts. Many are having problems installing new aftermarket mounts that don't fix the problem. The transmission mount get rocks stuck in it. This takes away the ability of the transmission mount to dampen vibration. This is due to the angle of the mount that makes it catch rocks from the road while you are driving.
The mounts are the most common if not main issue causing vibrations. It is possible, and I have seen such issues on other GM vehicles, for the harmonic balancer to create vibration problems. But as far as I know, I have not seen it or heard of another having vibration problems due to the harmonic balancer. The engine and transmission mounts are the main culprit on your vehicle.
I recommend the following inspection to help you out. Car is shaking and vibrating inspection
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